1. Field of the Invention
The present invention relates to a mixer-circuit-and a mobile terminal using same and, more particularly, to a quadrature mixer which performs signal frequency conversion, using two local equal-frequency signals with a 90 degree phase difference, and a mobile terminal using such a mixer.
2. Description of the Prior Art
Grounded on semiconductor circuit technology improvements, taking advantage of a merit of semiconductor circuits (although there is dispersion of absolute values of constants of parts among semiconductor chips, relative values of constants of parts within one semiconductor chip are matching with a high accuracy), wireless signal processing circuit topologies which dispense with a SAW filter and a dielectric filter have been proposed. Such topologies include a zero-IF receiver, near zero IF receiver, and wide band IF receiver. Any of these receivers does not need an external SAW filter and dielectric filter and suppresses unwanted signals falling out of a desired bandwidth with filters that can be built on a semiconductor device (some wireless communication method or system requirements may specify that the above-mentioned receivers should have some external filter).
The zero-IF receiver, near zero IF receiver, and wide band IF receiver feature a common characteristic configuration of a mixer circuit which performs signal frequency conversion. This mixer is called a quadrature mixer and its example is provided in FIG. 1 “Merged LNA and Mixer for 2.14 GHz direct conversion front-end” in a document (A. Karimi-Sanjaani, H. Sjoland and A. Abidi, “A 2 GHz Merged CMOS LNA and Mixer for “WCDMA”, In Digest of Tech. Papers VLSI Symposium 2001, June 2001, pp. 19-22, Tokyo, Japan).